Currently, network connectivity for mobile devices such as mobile telephones are provided by an operator. The network connectivity can involve the use of systems, such the general packet radio service (GPRS), that allow information to be sent and received across a mobile telephone network. It may be desirable for a server to be placed on that mobile device, where the server can be accessible by clients running on devices on the Internet.
In such a system, however, there are currently a number of obstacles that must be overcome. In current operator networks, mobile devices are assigned temporary Internet Protocol (IP) addresses. Client devices attempting to access a web server on such a device must therefore be provided with a way of reaching the server that is independent of the IP address that has been assigned to the mobile device. This constitutes a basic problem of addressability in such a system.
Even if a mobile device with a built-in server is assigned a static IP address, however, or if techniques such as dynamic domain name systems (DNS) are used, the server would still be inaccessible. This is due to the fact that operator firewalls typically do not allow connections to be created from a device on the Internet to a mobile device inside the operator's network. Instead, connections must be created from the inside of the operator's network and extend outward to the client device.
Although there have been attempts to address this accessibility issue, each of these proposed solutions possess serious shortcomings. One proposed solution involves port knocking. With port knocking, when certain firewall port numbers are knocked in a “secret” sequence, then one particular port number is opened for a short period of time. This concept is discussed at www.linuxjournal.com/article.php?sid=6811. Another solution involves the use of a firewall control protocol (FCP), which can enable a third, trusted party to dynamically control the firewall (i.e., which ports are opened, the period of time the ports are opened, which clients are permitted to have the ports opened, etc.) FCP is discussed at www.iptel.org/fcp/ietf-fcp.ppt. For both of these systems, however, there is a requirement that the out-of-network device be given at least some indirect control of the firewall. To satisfy this requirement, operators would need to invest more in their infrastructure and possibly attempt to solve a problem for which there is no correctly existing industry-standard. Moreover, making firewalls dynamically configurable would also result in a need to modify web browsers, which is undesirable.
In addition to the above, even if the mobile device possessing the server and the device from which the server is accessed are in the same operator network, there are still no guarantees that the server could be accessed, even if the client knows the temporary IP address. In particular, typical operators do not currently route packets directly between the mobile devices.